Commutator of the matrices of the rotation group

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Discussion Overview

The discussion revolves around the concept of commutators within the context of the rotation group ##SO(3)##. Participants explore the definitions and applications of commutators in relation to matrix representations of rotations.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant proposes that the expression ##R_{x}(\phi) R_{z}(\theta) - R_{z}(\theta) R_{x}(\phi)## can be considered a commutator.
  • Another participant expresses skepticism, stating that they have not seen the term "commutator" used for anything other than expressions of the form ##AB - BA##.
  • A different participant references a source, specifically Ryder's 'Quantum Field Theory', claiming it includes the term in a relevant context.
  • Another reply suggests consulting Wikipedia for a general understanding of commutators, implying that the question may have been addressed there.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the definition and application of the term "commutator" in this context, indicating multiple competing views remain.

Contextual Notes

There may be limitations in the definitions being used, as well as potential misunderstandings regarding the application of the term "commutator" in different mathematical contexts.

spaghetti3451
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Consider the rotation group ##SO(3)##.

I know that ##R_{x}(\phi) R_{z}(\theta) - R_{z}(\theta) R_{x} (\phi)## is a commutator?

But can this be called a commutator ##R_{z}(\delta \theta) R_{x}(\delta \phi) R_{z}^{-1}(\delta \theta) R_{x}^{-1} (\delta \phi)##?
 
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I haven't seen anyone use that term for anything other than expressions of the form AB-BA.
 
I found it in page 31 of Ryder's 'Quantum Field Theory' - second edition.
 

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